Lamps of motor vehicles produced at present use powerful light emitting diodes (LED's), which however heat up strongly during operation and issue high amounts of heat. The high temperature of LED's has a negative influence of the properties of semiconductors, which form the principal components of LED's. A higher working temperature reduces both the instantaneous luminous intensity of LED's and their service life. Therefore, intensive cooling of LED's is essential for proper functioning of light sources of the above mentioned type. What also needs to be provided is reliable mounting in the cooling monobloc and ingress protection of electric components. To reduce the temperature of LED's, coolers are used that are fixed to the structure of the lamp or the entire lamp body is used as a cooler. A commonly used material for a LED light source coolers is aluminum because it features high thermal conductivity, which ensures quick dissipation of heat from the heated part to other, colder parts.
Some designs are also known from, the prior art when the cooler of a light source is made of a thermally conductive plastic material. Thermal conductivity of a plastic material is substantially lower than that of an aluminum, cooler and the need to dissipate excessive heat is more urgent in the case of plastic material. Excessive heat is also dissipated from the light source by transfer to the ambient air. Due to high demand of the cooling media the cooling system must be equipped with a powerful cooling media source, e.g. a fan. On the other hand, plastic-based materials make it possible to produce complex components by compression moulding with good dimensional tolerances and very good surface finish. Another advantageous property is their design flexibility, which eliminates the need of final treatment of the surface and many assembly operations.
The document EP2187121 discloses a cooler of the light sources of optical modules of lighting devices of motor vehicles arranged next to each other, comprising optical modules arranged next to each other, each of them comprising a plate holder with a planar light source. The plate holders of the optical modules arranged next to each other are mutually connected with thermally conductive bridges for better temperature distribution and the thermally conductive bridges are equipped with cooling fins for heat dissipation. The plate holders of the planar light sources and the cooling fins form cooling monoblocs. The cooling fins are cooled by the ambient air. A disadvantage is a complex design of the cooler and insufficient dissipation of heat from the light source. A disadvantage of this design is also the fact that it uses a material with high thermal conductivity, which is associated with high financial demands. Also, the possibilities of the metal working technology are limited. The limited possibilities of the technology of machining of highly thermally conductive materials have a significant impact on the final shape and structural arrangement of the cooler. It is often necessary to adapt, the other components of the lighting device to the shape and dimensions of the cooler.
The document FR2996905 discloses a light device for motor vehicles with flat LED light sources mounted for heat distribution on a thermally conductive plate made of a plastic material with higher thermal conductivity than 1 W m−1° K.−1. To improve cooling of the thermally conductive plate the plate is fitted with a row of cooling fins arranged next to each other on the side that is averted from the light source. However, the efficiency of heat dissipation is very low as the light sources are cooled by mere blowing of air over the light sources and the other side of the thermally conductive plate is not exposed to streaming air.
The goal of the invention is a cooler of a planar light source that will have higher efficiency of heat transfer from the light source to the cooling media, and that will dissipate more heat from the light source on the whole. The goal of the invention is further such an arrangement of the cooler of the planar light source that will enable an easy replacement of the light source, easy association of the lamp reflector and cooling media source, and that will have a cooling monobloc with an integral and compact design. Also, the goal of the invention is to improve concentration of the streaming cooling media around the light source. Finally, the final goal of the invention is to achieve a simple design of the cooler of the planar source and shape flexibility of its parts during production.